Immune System Flashcards
What is the immune system?
An organised system of organs, cells and ,molecules that interact to defend the body against disease.
What are microbes?
Bacteria, viruses, fungi and protozoa
Name the organs of the immune system?
Tonsils Thymus Spleen Lymph nodes Bone Marrow
What is the role of primary lymphoid organs and what organs does this include?
primary production of white blood cells (leukacytes) includes the Bone marrow and thymus
What is the role of Secondary lymphoid organs and what organs does this include?
Site where immune responses are initiated. Includes Spleen, Tonsils and Lymph nodes
Function of Bone Marrow?
Source of stem cells that develop into cells of the innate and adaptive immune responses
Function of Thymus?
School for white blood cells called T cells, developing T cells learn not to react to self
Function of spleen?
Site of initiated immune responses against blood-bore pathogens
Function of Lymph Nodes
Filters Lymph fluid from blood and tissue
What is the Epidermis?
Outer layer of skin, dead cells, keratin and phagocytic immune cells
What is the Dermis?
Inner layer of skin, Thick layer of connective tissue,
collagen and blood vessels and phagocytic immune cells
What are chemical defenses of the skin?
Antimicrobial peptides (skin defensins)
Lysozyme: breaks down bacterial cell walls
Sebum: Low pH
Salt; Hypertonic
What is the Mucosal membrane?
1-2 layers, predominantly Epithelium: tightly packed live cells, constantly renewed, mucus-producing goblet cells
Where are mucosal membranes?
Mucosal membranes line parts of the body that lead to the outside and are exposed to air
Chemical defenses of Mucosal membranes?
Stomach – low pH Gallbladder – bile Intestine – digestive enzymes Mucus Defensins Lysozyme (tears, urine)
External surface barriers of Innate defenses?
Skin
Mucosal membranes
Internal barriers of innate defenses?
Phagocytes Natural Killer cells Inflammation Antimicrobial proteins Fever
Adaptive Defenses include?
B cells and T cells
Features of the innate immune response?
Already in place Rapid (hours) Fixed Limited specificities (detects molecular components shared by many pathogens) Has no specific memory
Features of the adaptive immune response?
Improves during the response Slow (days à weeks) Variable Highly specific (detects molecular components specific to individual pathogens) Has memory
What are blood cell lineages?
All blood cells develop from hematopoietic stem cells in
the bone marrow. These stem cells give rise to different lineages of cells, Myeloid; containing granulocytes,
monocytes, dendritic cells, platelets. (Innate immune cells.) or Lymphoids; containing B and T cells (all adaptive immune cells.)
What cells are granulocytes?
Neutrophils which are highly phagocytic cells that circulate in the blood. Numbers increase during infection and these cells can move into tissue during inflammation
Mast Cells which line mucosal surfaces and release granules that attract white blood cells to areas of tissue damage.
Relationship between monocytes and macrophages?
Monocytes are present in blood (low phagocytosis) until they leave to develop into macrophages in tissues eg, spleen and liver (high phagocytosis)
What are the important roles of macrophages?
Phagocytosis
Release of chemical messengers
Show information about pathogenic microbes to T
cells (linking innate and adaptive immunity)
What are the important functions of dendritic cells?
Linking innate and adaptive immune responses
Phagocytosis
Triggers adaptive immune responses
How do innate cells recognise pathogens?
PAMPS in the common building blocks of microbes.
Toll like receptos.
How is fever induced?
Abnormally high temperature
resetting of thermostat (hypothalamus)
pyrogens released my immune cells
Phagocytes produce the chemical messenger and
pyrogen interleukin-1
decreased phagocytosisà = decreased IL-1 à = decreased temperature
Describe the key components of the inflammatory response?
Neutrophils enter blood from bone marrow
Cling to capillary wall
chemical signals dilate blood vessels and make capillary wall leakier
Neutrophils squeeze through leaky capillary wall and follow signals to injury site
Describe the five stages of phagocytosis.
Bind Engulf Fuse Destroy Exocytosis
What is the compliment cascade?
Compliment = 9 major proteins/protein complexes
(C1-9) act in sequence to clear pathogens from
blood and tissues
What is an antigen?
a toxin or other foreign substance which induces an immune response in the body, especially the production of antibodies
Describe the process of antigen sampling and presentation?
Dendritic cells phagocytose antigen and process it down to peptides.
They then migrate from organs to draining lymph nodes.
They present peptides on MHC to T cells.
What is the role of CD8 and CD4 T cells>
CD4 T cells help B cells make antibody.
CD8 T cells become cytotoxic and kill virus
infected cells and cancer cells.
what is the purpose of clearing antigens?
Clearance of pathogens (Innate) and for presentation to T cells (adaptive)
How are invertebrates and vertebrates different?
Vertebrates have both an innate and adaptive immune stem whereas invertebrates only have innate
What was the beginning of the adaptive immune response?
Phagocytes evolved to keep remnants of pathogens and display these to other cells of the immune system.
How does MHC expression vary?
MHC-I presents endogenous (intracellular) antigen.
Expressed on all nucleated cells. Whereas MHC-II presents exogenous (extracellular) antigen.
Expressed only on antigen presenting cells
What does MHC stad for?
Major Histocompatibility complex, molecules.
What is the process of MHC-I antigen processing?
Antigenic proteins are degraded to peptides in the cytoplasm, peptides are the imported to the ER, followed by the loading of MHC-1 which takes place in the ER before they are transported to the cell surface.
What is the process of MHC-II antigen processing?
Antigenic proteins are degraded in acidic phagolysosome, then peptide loading of MHC-II takes place in the phagolysosome before it is bought to the surface.
What is an antigen presenting cell??
(APCs) are the cells that link the innate immune response with T cell and B cell responses
What are the functions of APCs?
Take up proteins from pathogens and process them into antigens.
live all over the body, ready to meet a pathogens.
present antigens on MHC to T cells, that then become activated.
The best APCs are dendritic cells
What are T Cells?
T cells are lymphocytes that are specific for a particular antigen.
What are the function s of T cells?
• T cells get activated by APCs and then proliferate and
make cytokines and cytotoxic molecules
• T cells can destroy pathogens and also help other
immune cells destroy pathogens
• There are two types of T cells – CD4 T cells and
CD8 T cells
Examples of endogenous antigens?
Viral proteins produced during viral replication.
Proteins produced by intracellular bacteria such as listeria.
Examples of Exogenous antigens?
Fungi, bacteria, parasites.
What receptors do T cells have?
T cells express T cell receptor (TCR) , each Cell has a specific TCR for one specific antigen peptide. Each T cell also has a co- receptor either CD4 or CD8. T cells recognise MHC.
What happens to T cells in bone marrow>
Where T cell precursors are produced and T cells are created.
What happens to T cells in the thymus?
TCR gene rearrangement.
Make T cells able to recognise antigen.
Get rid of T cells that recognise self antigen.
What is the purpose of gene rearrangement in the thymus?
- This ensures that each individual T cell has a unique TCR
* Creates diversity in T cell repertoire = can recognise all types of pathogens
How do CD4 T Cells differ from CD8 T cells?
- CD4 T cells recognise peptide antigen in context of MHC II
- CD8 T cells recognise peptide antigen in context of MHC I
- CD4 T cells make cytokines to support other immune cells Helper T cells
- CD8 T cells make cytotoxic molecules to kill infected cells Cytotoxic T lymphocytes (CTL)
What do activated T cells do (effector T cells) ?
kill infected cells
make cytokines
support antibody production
remember the antigen for next time
What are memory T cells?
T cell activation results in the formation of memory T cells. Memory CD4 or CD8 T cells reside in the body for long periods of time
What are B cells?
Lymphocytes that develop in the bone marrow,.
What do B Cells do?
Express BCR, activate plasma cells that secrete antibody and some memory B cells provide memory.
Where do B cells develop?
one marrow and thymus
Where does B cell activation occur?
Lymph Nodes and spleen
What does a BCR do?
The surface of B cells are covered in BCRs. They bind antigens which activates the B cell and tuns it into a plasma cell which secretes antibodies.
What are the functions of antibodies?
Neutralization, Opsonisation, Activation of compliment
What are isotypes?
Types of antibodies. Different types of isotyes are important for different times of immune response, sites of infection and types of pathogens.
What do memory cells do/
persist of years in blood and lymph.
Express antibody as BCR but do not secrete antibody.
If they see the same antigen again they respond rapidly to become plasma cells.
What is the Primary Immune response?
Involves naive B cells.
1-2 weeks to eliminate pathogen.
Low amount of antibody produced, mainly igM.
What is the secondary Immune response?
Relies on memory cells.
2-3 days to eliminate pathogen.
Higher amount of antibody produced.
Basis of vaccination.
What is the overall aim of the innate immune system?
Preventing opportunistic microbes from entering the body. Therefore it targets adherence, invasion and the beginning of replication.
Role of Cilia?
Cilia in our airways clumps bacteria and spores, the rhythmic beating brings the mucus up to release it.
What do defensins do?
excreted by the cell, they land on surfaces of bacteria and bind the to charged surface of microbial membranes which disrupts these bilipid membranes.
What does lysozyme do?
Active against gram positive bacteria. Lysozyme breaks the bonds between glycopeptides by breaking links between the sugars causing the cell walls to collapse and die.
Where is lysozyme produced
tears and breast milk
Is the compliment system innate or adaptive?
It is a combination of both. The alternative and lectin pathways are part of the innate response whilst the classical pathway is adaptive.
What are the benefits of the adaptive immune response?
Active against all microbes and able to target intracellular microbes at every stage of pathogenesis which fights infection and disease.
What cells arise from rapid expansion?
Cytotoxic T cells, CD4 Helper T cells, Memory T cells.
Why is co-stimulation of MHC-I and II necessary?
In order to make CD8 T cells.
What is required for a plasma cell to from?
Hel from CD4 T cells.
What is Skid?
A disease whereby a person does not have any B or T immune cells and therefore has a very short life expectancy.
What is Rheumatoid Arthritis?
An autoimmune disease caused by a hyperactive immune system that attacks self tissue and cells and specifically the synovial membrane.
How do Allergies arise?
Dendritic cells in the immune system mistake allergens for microbes ie, viruses that then develop into an immune responses.
What antibodies are produced from allergic reactions?
IGE which is produced from activated plasma cells
What does IGE do when it is released?
Binds to the surface of mast cells through FCE receptors on mast cells.
What chemical is released from capsules in mast cells
Histamines, which trigger an immediate allerric reaction response
What are type 1 hypersensitivity reactions?
Allergic reactions
